Backpack



FIG. 1 is a front perspective view of a backpack showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a side view thereof;

FIG. 5 is an opposite side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines immediately adjacent to the shaded area represent unclaimed boundaries of the design. The broken lines showing the remainder of the backpack represent unclaimed subject matter and form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 